There are many situations in which it is desirable to identify a person. For example, many forms of payment today require customers to provide a form of authentication to a store, e.g., when paying with a credit card, the customer needs to be able to reproduce the signature found on the back of the card. This constitutes a weak form of identification. If the transaction has a high monetary value, the customer may be required to provide additional forms of identification, such as a driver's license. Similarly, employers may issue “food cards” to their employees that serve to authenticate the employees when making a purchase, and link their identity to an account from which money for the purchase can be deducted.
Card presentation and verification schemes, along with checking signatures and/or government-issued photo IDs, are subject to errors on the part of the merchant's clerk or the like. Such schemes also require non-negligible effort on the part of the customer, e.g., remembering to bring a card, a photo identifier, carefully signing and so forth.
A different to ascertain a person's identity is through the use of biometrics, including face recognition, retinal and/or iris scanning, fingerprint reading, voice identification and so forth. However, many forms of biometrics are invasive; for example, it is not reasonable to ask an employee to subject himself or herself to short-range iris scanning to buy lunch, (nor is it currently practical from an expense and maintenance perspective). At the same time, contemporary non-invasive types of biometrics such as face recognition technology are not sophisticated enough to provide the level of accuracy that is needed for a payment scheme.
What is desirable is an identification scheme that requires virtually no effort on the part of the identified person. At the same time, to be useful such a scheme needs to be reasonably practical, non-invasive, secure and accurate.